The present invention generally relates to a high speed print head for an inkjet printer which involves the integration of stressed thin film technology having improved print quality, print speed, and lower cost.
In prior art, ink jet print heads have been developed using heat to eject drops of ink fluid. Thermal ink jet print heads include an ink reservoir in a fluid communication with a print head substrate having a plurality of resistors. The resistors, conventionally, exist in an electrically conductive layer which is positioned on selected periods of the layer of resistive material. Selective electrical activation of the resistors causes a rapid boiling of the ink in the proximity of the activated resistors and expulsion of the ink from orifices (print head nozzles) in the print head. In all such print head devices, a major disadvantage is that after use, the heater elements accumulate residue from the boiled ink which reduces the heat transfer from the heater elements to the ink, in conjunction with clogging the nozzle jets. As a result, the consistency of print quality will be affected. Another major disadvantage is that the ink must be water based which reduces the printer's compatibility with different ink types.
In other prior art, piezoelectric elements are used to produce an improved printing system. A piezoelectric print head usually comprises a fluid chamber supplied with fluid ink and having a nozzle orifice. A piezoelectric element array is mounted adjacent to the fluid chamber. Selective operation of the printing apparatus is provided by energizing the piezoelectric elements in response to an electrical signal to reduce the volume in the fluid chamber and to force a single drop of ink from the nozzle orifice to be ejected. A major disadvantage of this system is that the piezoelectric element must have a large surface area to displace enough ink volume, since the piezoelectric elements which deform upon application of a voltage have a very small displacement. This results in a large cumbersome size with a high cost of manufacturing.
To resolve these problems, a modern design of high speed print head is provided. This new design increases the printing speed and quality, improves the ink flow and eliminates the print head nozzles clogging, thus ensuring compatibility with different ink types and reducing the print head sizes and cost.